1. Field of the Invention
The present invention relates to a telescopic device of a steering column for a vehicle, which adapts the steering column for the vehicle to have a telescopic motion, and more particularly, to a telescopic device of a steering column for a vehicle, in which a telescopic bush is provided at an internal tube.
2. Discussion of Related Art
A steering apparatus which allows a driver to change a vehicle's moving direction to a desired direction includes a steering shaft which allows a rotational force generated from a steering wheel to be transmitted to a gear box and a tie rod.
Generally, the steering shaft enables transmission of the rotational force and axial expansion and contraction even in a state in which the steering shaft is inclined at a predetermined angle. A steering column which supports the steering shaft and also fixes the steering shaft to a vehicle body is installed at an outer circumferential surface of the steering shaft.
Particularly, the steering column includes a tilt device and a telescopic device which enable a position of the steering wheel to be adjusted according to a driver's body condition. The telescopic device serves to allow the steering shaft to be slid in a lengthwise direction and thus to enable the steering column to be adjusted in the lengthwise direction.
FIG. 1 illustrates a conventional telescopic device. Referring to the drawing, in the telescoping device, an external tube 20 is formed on an outer side of an internal tube 10 to be moved forward and backward in a lengthwise direction. At this time, a tilt bolt 30 of a tilt device is provided to pass through a through-hole 22 formed in both sides of the external tube 20.
Therefore, the external tube 20 may be moved by a front and rear length of the through-hole 22, and organically connected with the tilt device.
However, in the conventional telescopic device, friction may occur between the tilt bolt 30 and an inner surface of the through-hole 22 of the external tube 20. Therefore, a noise may be generated by the friction between the tilt bolt 30 and the inner surface of the through-hole 22, and also components may be rapidly worn.
Meanwhile, in order to prevent the physical wear of the device, an elastic telescopic bush 25 was provided at the inner surface of the through-hole 22 of the external tube 20. However, since the friction was more increased due to the elastic material, the telescopic bush 25 itself was rapidly worn, and thus a repair work was frequently required.
Therefore, a new method to overcome these problems is required.